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Computers RSS FeedsCapsule Reviews - The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. ...Feed Source: comjnl.oxfordjournals.org On the Acceleration of Wavefront Applications using Distributed Many-Core Architectures -
In this paper we investigate the use of distributed graphics processing unit (GPU)-based architectures to accelerate pipelined wavefront applications—a ubiquitous class of parallel algorithms used for the solution of a number of scientific and engineering applications. Specifically, we employ a recently developed port of the LU solver (from the NAS Parallel Benchmark suite) to investigate the performance of these algorithms on high-performance computing solutions from NVIDIA (Tesla C1060 and C2050) as well as on traditional clusters (AMD/InfiniBand and IBM BlueGene/P). Benchmark results are presented for problem classes A to C and a recently developed performance model is used to provide projections for problem classes D and E, the latter of which represents a billion-cell problem. Our results demonstrate that while the theoretical performance of GPU solutions will far exceed those of many traditional technologies, the sustained application performance is currently comparable... Performance Characteristics of Hybrid MPI/OpenMP Implementations of NAS Parallel Benchmarks SP and BT on Large-Scale Multicore Clusters -
The NAS Parallel Benchmarks (NPB) are well-known applications with fixed algorithms for evaluating parallel systems and tools. Multicore clusters provide a natural programming paradigm for hybrid programs, whereby OpenMP can be used with the data sharing with the multicores that comprise a node, and MPI can be used with the communication between nodes. In this paper, we use Scalar Pentadiagonal (SP) and Block Tridiagonal (BT) benchmarks of MPI NPB 3.3 as a basis for a comparative approach to implement hybrid MPI/OpenMP versions of SP and BT. In particular, we can compare the performance of the hybrid SP and BT with the MPI counterparts on large-scale multicore clusters, Intrepid (BlueGene/P) at Argonne National Laboratory and Jaguar (Cray XT4/5) at Oak Ridge National Laboratory. Our performance results indicate that the hybrid SP outperforms the MPI SP by up to 20.76%, and the hybrid BT outperforms the MPI BT by up to 8.58% on up to 10 000 cores on Intrepid and Jaguar. We also... Performance Analysis and Optimization of the OP2 Framework on Many-Core Architectures -
This paper presents a benchmarking, performance analysis and optimization study of the OP2 ‘active’ library, which provides an abstraction framework for the parallel execution of unstructured mesh applications. OP2 aims to decouple the scientific specification of the application from its parallel implementation, and thereby achieve code longevity and near-optimal performance through re-targeting the application to execute on different multi-core/many-core hardware. Runtime performance results are presented for a representative unstructured mesh application on a variety of many-core processor systems, including traditional X86 architectures from Intel (Xeon based on the older Penryn and current Nehalem micro-architectures) and GPU offerings from NVIDIA (GTX260, Tesla C2050). Our analysis demonstrates the contrasting performance between the use of CPU (OpenMP) and GPU (CUDA) parallel implementations for the solution of an industrial-sized unstructured mesh consisting of a... SST: A Scalable Parallel Framework for Architecture-Level Performance, Power, Area and Thermal Simulation -
In this paper, we describe the integrated power, area and thermal modeling framework in the structural simulation toolkit (SST) for large-scale high performance computer simulation. It integrates various power and thermal modeling tools and computes run-time energy dissipation for core, network on chip, memory controller and shared cache. It also provides functionality to update the leakage power as temperature changes. We illustrate the utilization of the framework by applying it to explore interconnect options in manycore systems with consideration of temperature variation and leakage feedback. We compare power, energy-delay-area product (EDAP) and energy-delay product (EDP) of four manycore configurations-1 core, 2 cores, 4 cores and 8 cores per cluster. Results from simulation with or without consideration of temperature variation both show that the 4-core per cluster configuration has the best EDAP and EDP. Even so, considering that temperature variation increases total power ... Benchmarking Energy Efficiency, Power Costs and Carbon Emissions on Heterogeneous Systems -
With the advent of heterogeneous computing systems consisting of multi-core central processing units (CPUs) and many-core graphics processing units (GPUs), robust methods are needed to facilitate fair benchmark comparisons between different systems. In this paper, we present a benchmarking methodology for measuring a number of performance metrics for heterogeneous systems. Methods for comparing performance and energy efficiency are included. Consideration is given to further metrics, such as associated running costs and carbon emissions. We give a case study for these metrics applied to Bristol University Docking engine, a molecular mechanics-based docking application that has been ported to open computing language at the University of Bristol. Results are included for both AMD and NVIDIA GPUs, and for a highly optimized code on the latest x86 CPUs.
... Memory Trace Compression and Replay for SPMD Systems Using Extended PRSDs -
Concurrency levels in large-scale supercomputers are rising exponentially, and shared-memory nodes with hundreds of cores and non-uniform memory access latencies are expected within the next decade. However, even current petascale systems with tens of cores per node suffer from memory bottlenecks. As core counts increase, memory issues will become critical for the performance of large-scale supercomputers. Trace analysis tools are thus vital for diagnosing the root causes of memory problems. However, existing memory tracing tools are expensive due to prohibitively large trace sizes, or they collect only statistical summaries and omit potentially valuable information. In this paper, we present ScalaMemTrace, a novel technique for collecting memory traces in a scalable manner. ScalaMemTrace builds on prior trace methods with aggressive compression techniques to allow lossless representation of memory traces for dense algebraic kernels, with near-constant trace size irrespective of th... Leveraging Service Discovery in MANETs with Mobile Directories -
This paper advances a novel approach that facilitates the location of services and/or digital assets advertised by directories in a Mobile Ad hoc Network. The proposed Service Directory Placement Protocol (SDPP) improves scalability and reduces packet traffic overhead by advancing a multi-directory extension of an earlier approach that relied on the migration of a single directory through the network. This investigation demonstrates that modelling the directory replication problem as a Semi-Markov Decision Problem solved by means of a Reinforcement Learning technique known as Q-learning improves the performance of SDPP. Computer simulations validate the feasibility of the proposed scheme that enables packet overhead reductions between 15 and 75 %, whereas the directory location success rate improves by up to 11% when compared with pure broadcast flooding and other existing approaches in wireless networks where hosts move at walking speeds.
... Evaluation of a Java Ahead-of-Time Compiler for Embedded Systems -
Java embedded systems often include Java middleware classes installed on the client device. For higher performance, they can be compiled into machine code before runtime using an ahead-of-time compiler (AOTC). There are many approaches to AOTC, yet a bytecode-to-C (b-to-C) AOTC which translates the bytecode into the C code and then compiles it using an existing optimizing compiler such as gcc would be the most straightforward one. This paper explores a few important design and optimization issues of a b-to-C AOTC, including the compilation form for the translated C code, the call interfaces among translated and interpreted Java methods, and Java-specific optimizations by the AOTC that can complement the gcc optimizations. We evaluate these issues with our b-to-C AOTC implemented on the MIPS platform for the Sun's CDC VM to understand their performance impact.
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Forensic scientists in the U.S. are applying DNA fingerprinting methods to the cannabis plant. They say the technique, which is being used to create a database of DNA profiles of different marijuana plants, will help them to trace the source of any sample.
'It links everybody together: the user, the distributor, the grower,' says the database's creator, Heather Miller Coyle of the Connecticut State Forensic Science Laboratory in Meriden. 'That's the real intent of it, to show it's not just one guy with a little bag of marijuana, but it's a group of people.'
A method for spotting the tiniest traces of marijuana, based on detecting DNA unique to cannabis chloroplasts, has already been developed in the UK (New Scientist print edition, 07 Aug 1999). B... Mathematics: Does the Proof Stack Up? - by George Szpiro
03 Jul 03
Just under five years ago, Thomas Hales made a startling claim. In an e-mail he sent to dozens of mathematicians, Hales declared that he had used a series of computers to prove an idea that has evaded certain confirmation for 400 years. The subject of his message was Kepler's conjecture, proposed by the German astronomer Johannes Kepler, which states that the densest arrangement of spheres is one in which they are stacked in a pyramid - much the same way as grocers arrange oranges.
Soon after Hales made his announcement, reports of the breakthrough appeared on the front pages of newspapers around the world. But today, Hales's proof remains in limbo. It has been submitted to the prestigious Annals of Mathematics, but... Scientists Discover Planetary System Similar to Our Own -
The image shows an impression by David A. Hardy of a possible scene from a moon orbiting the extra-solar planet in orbit around the star HD70642. Photo Credit: David A. Hardy.
... Hacker How-To Good Summer Reading - by Michelle Delio
27 Jun 03
Stealing the Network: How to Own the Boxby Ryan RussellSyngress, 330 pp., $49.95
Stealing The Network: How to Own the Box, a compendium of tales written by well-known hackers, is a perfect summer read. The stories are fictional. The technology and techniques described are very real.
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